We propose to further characterize the DNA transformation system recently discovered in the blue-green alga (cyanobacterium) Agmenellum quadruplicatum strain PR-6. Competence, DNA eclipse, DNA-DNA uptake competition, efficiency of DNA uptake, and DNA size dependence will be characterized. Heterospecific transformation of various blue-green algae will be done in hopes of ascertaining phylogenetic relationships between these organisms. Auxotrophic and pigment mutants will be isolated by in vivo and in vitro mutagenesis techniques using chemical mutagens. These mutants will be used to begin the development of a genetic map of the PR-6 chromosome. The genetic framework established by the genetic map will be further elaborated through use of a PR-6 gene bank established in an Escherichia coli plasmid.